1. Technical Field
The present invention relates to a stepping motor control circuit, a semiconductor device including the stepping motor control circuit, and an analog electronic timepiece including the stepping motor control circuit.
2. Related Art
A chronograph timepiece has been used as an analog electronic timepiece having time hands for displaying the current time and chronograph hands for displaying a measured time length (a chronograph 1/10-second hand for display on a 1/10-second basis, a chronograph second hand for display on a 1-second basis, and a chronograph minute hand for display on a 1-minute basis).
A chronograph timepiece has a reset function for resetting each of the chronograph hands to return to the zero position after measurement is completed or in response to reset button operation. For example, JP-A-2004-2266078 introduces a chronograph timepiece having the following functions set therein and performed when the reset function is used: a function of forward rotation reset in which the chronograph hands are rotated in the forward direction (clockwise, for example) at the time of reset and reverse rotation reset in which the chronograph hands are rotated in the reverse direction (counterclockwise, for example) at the time of the reset.
The chronograph timepiece described in JP-A-2004-2266078 includes a stepping motor that is driven stepwise based on inputted drive pulses to move the chronograph hands (indicating hands) described above and a stepping motor control circuit that controls the stepping motor. The stepping motor control circuit includes a drive pulse generation section that generates forward-rotation drive pulses that drive the stepping motor stepwise in the forward direction and reverse-rotation drive pulses that drive the stepping motor stepwise in the reverse direction and a forward/reverse rotation switching control section that performs switching control in which the drive pulses outputted to the stepping motor are switched from one of the forward-rotation drive pulses and the reverse-rotation drive pulses to the other.
In the chronograph timepiece described in JP-A-2004-2266078, however, when the chronograph hands are reset, for example, by pressing a reset button, the chronograph hands can move in a reset rotation direction abnormally depending on the timing at which the reset button is pressed. That is, assuming that the stepping motor moves the chronograph hands in the forward rotation direction in normal operation whereas moving them in the reverse rotation direction at the time of reset, switching the normal-rotation drive pulses in the course of one cycle thereof to the reverse-rotation drive pulses, which drive the chronograph hands in the reset rotation direction, causes the timing at which the hands start being moved in the reverse rotation direction to be shifted, undesirably resulting in abnormal hand movement or what is called a hand movement error.